304 Transactions. 



Art. XXXI. — The Vegetation oj the Tarawera Mountains, New Zealand. 



By B. C. Aston, F.I.C, F.C.S. 

 [Bead before the Wellington Philosophical Society, 27th October, 1915.] 



Plates XIX-XXII. 



Introduction. 



On the 10th June, 1886, New-Zealanders were startled from their quiet 

 lives by a volcanic eruption, the sounds of which reached from three to four 

 hundred miles north and south from the seat of the outburst, while the 

 ashes fell over an area variously estimated at from four thousand to six 

 '"housand square miles. The greatest depth of the matter ejected, measured 

 -it the lip of the great vent, was 170 ft., the top of the range being increased 

 oy this amount. It has. been estimated that from two-fifths to one cubic 

 mile of material was thrown out. The eruption took place along a flat- 

 topped range, 3,600 ft. altitude, composed of rhyolitic lava-flows, known as 

 Tarawera Mountains, and comprising the peaks Wahanga (northernmost), 

 Ruawahia, and Tarawera (southernmost). This range is situated on the 

 eastern side of Lake Tarawera, in the thermal district of the North Island, 

 where are situated Lakes Rotorua and Taupo, well known as tourist resorts. 

 A gigantic rent opened along the axis of the range, running roughly 

 north-east and south-west, commencing at the north end and extending 

 to Tarawera, thence in a line more westerly to Lake Rotomahana, the waters 

 of which are thought to have caused further explosions. This rent finally 

 ended at Lake Okaro in the south, taking but three or four hours to form. 

 Along this immense chasm in the earth, nearly nine miles long, 900 ft. deep 

 at its greatest and 300 ft. at its least depth, and a mile and a half to an 

 eighth of a mile wide, were no fewer than seventeen points of eruption. 

 The fissure is not continuous, but is bridged in several places by the original 

 surface remaining in position. This titanic feature of the North Island 

 thermal district is at the highest points certainly the most impressive of 

 the sights, and probably the least Adsited by tourists. 



The north-western face of the Tarawera Range at present rises from the 

 shores of Lake Tarawera (which is 1,032 ft. above sea-level) to a height 

 of 2,738 ft. above it, the summit of the range being 3,770 ft. above the sea. 

 S. Percy Smith (2, -i. and 23), who had the advantage of thoroughly explor- 

 ing the mountain both before and after the eruption, describes the contour 

 of the mountain as being unUke any other in the district, with the plateau- 

 Vike summit sloping down to, say, 400 ft. ; the steep " mural crown" below 

 descending for, say, another 400 ft.; the sharply inclined talus at an angle 

 of 30° extending 1,000 ft. below the rock-faces forming the " mural crown " ; 

 and the beautifully easy slopes, lowest of all, grading down to the lake- 

 margin as a pumice beach or ending in low cliffs at the water's edge. 

 This is a fair average of the aspect it presents on every side, except 

 towards the east, where a range of less elevation joins it and spoils its 

 symmetry. The forests which once clothed the slopes of this mountain, 

 according to the above authority, were of considerable extent, especially 

 over the south-eastern flanks — that is, on the opposite side of the range to 

 those described in this paper. The eruption has utterly destroyed these 

 forests. Instances of a totara {Podocarpus totara) and rimu (Dacrydium 

 cupressinum) standing on the edge of the chasm are given (2, p. 52). 



A. P. W. Thomas (11) has written perhaps the most comprehensive report 

 of the eruption, although he had not the advantage of having visited the 



